1. Field of the Invention
The present invention relates to a display base including a torque limiter and the torque limiter.
2. Description of the Background Art
A torque limiter applied to a display base comprising a driving source turning a display screen portion and a transmission gear portion for transmitting the driving force of the driving source to a turning portion is know in general, as disclosed in Japanese Patent Laying-Open Nos. 7-190083 (1995), 2004-360809, and 6-11016 (1994), for example.
The aforementioned Japanese Patent Laying-Open No. 7-190083 discloses a torque limiter comprising a rotating member (second member) having a contact surface in a rotational direction and rotating integrally with a shaft, a driving gear plate having a contact surface at a position to be opposed to the contact surface of the rotating member and provided coaxially rotatably with the rotating member, a pressure spring (helical compression spring), a press plate urged by the pressure spring, an adjusting ring for adjusting the pressing force of the pressure spring and two slide plates held between the rotating member, the driving gear plate and the press plate respectively. In this torque limiter, a driving torque of the driving gear plate adjusted to a prescribed value is transmitted to the rotating member through the slide plate held between the driving gear plate and the rotating member with the pressing force of the pressure spring (helical compression spring) and rotation of the driving gear plate is not transmitted to the rotating member by slip of the slide plates at a constant driving torque or more.
The aforementioned Japanese Patent Laying-Open No. 2004-360809 discloses a gear with a torque limiter comprising two major-diametral gear and minor-diametral gear receiving a rotating shaft and so provided as to be opposed to each other, four steel balls rotatably arranged in the major-diametral gear, two friction discs holding the four steel balls therebetween from both sides of the major-diametral gear, and a spring engaging the minor-diametral gear with one of the friction discs of the major-diametral gear to allow transmission of the driving torque and elastically urging the minor-diametral gear to the major-diametral gear. In this gear with a torque limiter, the driving torque of the minor-diametral gear adjusted to a prescribed value is transmitted to the major-diametral gear through the two friction disc with the pressing force of the spring, while, when at a constant driving torque or more, rotation (driving torque) of the minor-diametral gear is not transmitted to the major-diametral gear by slip of the friction disc closer to the minor-diametral gear due to rotation of the four steel balls.
The aforementioned Japanese Patent Laying-Open No. 6-11016 discloses a torque limiter (viscous joint) comprising a minor-diametral gear (driving gear) directly connected with an impeller, a major-diametral gear (driven gear) having a storage portion (viscous fluid chamber) rotatably storing the impeller of the minor-diametral gear therein, viscous fluid sealed in the storage portion of the major-diametral gear with a mounting side plate fitted with an O-ring. In the viscous joint described in this Japanese Patent Laying-Open No. 6-11016, the impeller rotated with rotation of the minor-diametral gear (driving gear) causes swirling current in the viscous fluid of the major-diametral gear (driven gear), whereby the major-diametral gear is driven following rotation of the impeller through prescribed driving torque.
However, the conventional torque limiter proposed in the aforementioned Japanese Patent Laying-Open No. 7-190083 must be provided with a large number of members such as the adjusting ring for providing constant urging force to the pressure spring or the press plate urging the pressing force of the pressure spring. Therefore, in a case where the torque limiter described in Japanese Patent Laying-Open No. 7-190083 is applied to a base of display (liquid crystal display, for example) comprising a driving source turning a display screen portion and a transmission gear portion for transmitting the driving force of the driving source to a turning portion, the number of components of the transmission gear portion is disadvantageously increased.
The conventional torque limiter (gear with a torque limiter) proposed in the aforementioned Japanese Patent Laying-Open No. 2004-360809 must be provided with a large number of members such as the four steel balls rotatably arranged inside the major-diametral gear and the two friction disc holding the four steel balls from the both side of the major-diametral gear. Therefore, in a case where the gear with a torque limiter described in Japanese Patent Laying-Open No. 2004-360809 is applied to a base of display (liquid crystal display, for example) comprising a driving source turning a display screen portion and a transmission gear portion for transmitting the driving force of the driving source to a turning portion, the number of components of the transmission gear portion is disadvantageously increased.
The conventional torque limiter (viscous joint) proposed in the aforementioned Japanese Patent Laying-Open No. 6-11016 must be provided with a large number of members such as the viscous fluid, the O-ring for sealing the viscous fluid in the storage portion and the mounting side plate fitted with the O-ring. Therefore, in a case where the viscous joint described in Japanese Patent Laying-Open No. 6-11016 is applied to a base of display (liquid crystal display, for example) comprising a driving source turning a display screen portion and a transmission gear portion for transmitting the driving force of the driving source to a turning portion, the number of components of the transmission gear portion is disadvantageously increased.